This research plan proposes to contribute to the understanding of the subunit structure and function of oncornavirus RNAs. For the studies we will use as a model virus 377 avian sarcoma virus. The objectives and methods of this research are: 1) To determine the significance of methylation of viral RNA and its possible role in oncornavirus replication by a) locating the internal N6 methyladenosine residues and methylated oligonucleotides; b) determining the stoichiometry of the methylated oligonucleotides and c) determining the role of the host cell and virus in specifying the sites and extent of methylation. 2) To isolate RNA fragments derived specifically from the 5' terminus of viral RNA by dihydroxyborylaminoethyl-cellulose chromatography in order to a) determine whether the genome RNA subunits contain terminally redundant sequences; b) to characterize the ribosomal binding sites on the RNA. 3) To investigate the architecture of the 60 to 70 S genome RNA and the function of this structure by a) electron microscopy of crosslinked RNA; b) attempting to reconstruct the 60 to 70 S structure from 35 S RNA subunits. 4) To investigate virion age-dependent maturation and its role as a determinant of infection and endogenous reverse transcriptase activity. 5) To isolate, characterize viral-specific mRNAs from infected cells by immune precipitation of polysomes and to determine their relationship to viral genome RNA.